The invention relates to cylinder rings with mutually coordinated single-flight nut threads and bolt threads and with axial stop faces, running perpendicularly with respect to the cylinder axis, between the cylinder rings.
Cylinder rings of this type are used in precision mechanical and optical apparatus construction for the screw connection of components or accessories. A nut thread on the front side of photographic objectives serves, for example, for the reception of filters or shutters provided with a bolt thread. An objective may likewise be equipped with a bolt thread for insertion into a nut thread in the housing of a camera (JP 08043705 A Patent Abstracts of Japan).
The cylinder rings have axial stop faces which run perpendicularly with respect to the cylinder axis and which define how far said cylinder rings can be screwed one into the other. The stop faces may be provided on the end face of the nut thread or on the foot side of the bolt thread, or vice versa. By an appropriate dimensioning of the thread diameters, the stop faces can in each case be generated on the end face or on the foot side with respect to the thread flights on the cylinder rings. The stop faces are annular faces.
Screw fastenings for containers are known from DE 42 16 151 A1, DE 296 17 039 U1 and DE 79 16 575 U1. A closing cap with an internal thread and a corresponding external thread on the container are provided with radial stop faces which limit the rotational movement when the closing cap is screwed on in an end position.
Usually, the nut thread is the stationary part and the accessory is screwed with the bolt thread into the nut thread. In this case, there is often the requirement that the accessory should have a specific orientation with respect to its rotary position when the stop faces butt one against the other. In the case of an objective screwed into the camera housing, the lettering on adjusting rings should be legible from above in a normal posture. A pole filter screwed into an objective and an angular lens hood should be oriented automatically with respect to the image format.
The desired orientation of the rotary position cannot be achieved by means of simple threads on account of the relatively high tolerances in the engagement of the threads one into the other. The play in the thread flights which is necessary for an easy motion of the threads gives rise, when the stop faces are rotated firmly one against the other, to additional angular twists. Threads cut to the measurement point, as they are known, which allow an engagement of the threads which is fixed exactly radially, also possess tolerances of up to 5° in the rotary position until the stop faces are seated firmly.
For the fastening of accessories with an automatically exact rotary angle orientation, bayonet connections are therefore selected. These possess claws which hook on the counterpiece as a result of a rotational movement. Such bayonets consist of highly complicated milled parts and additionally require a spring ring for securing against unintentional loosening. An additional rotary stop ensures the desired rotary orientation. The components mentioned are complicated to produce and take up a relatively large construction space.